Dedicated outdoor air system with pre-heating and method for same

Abstract

A Dedicated Outdoor Air System (DOAS) includes a heater configured to be disposed within a supply air flow path, at least one pre-heater configured to be upstream from the heat exchanger within one or both of the supply and exhaust air flow paths, and a heat transfer device operatively connected to the heater and the pre-heater. The heat transfer device is configured to receive flue gas from the heater and transfer heat from the flue gas to liquid within the heat transfer device. The liquid is configured to be channeled to the pre-heater so that heat is transferred from the liquid to supply air within the supply air flow path.

What is claimed is: 
     
         1 . An energy exchange system comprising:
 an energy recovery device configured to be disposed within supply and exhaust air flow paths;   a heater configured to be disposed within the supply air flow path, wherein the heater is configured to generate flue gas;   at least one pre-heater configured to be upstream from the energy recovery device within one or both of the supply and exhaust air flow paths; and   a heat transfer device operatively connected to the heater and the at least one pre-heater, wherein the heat transfer device is configured to receive energy from the flue gas from the heater and transfer heat from the flue gas to liquid within the heat transfer device, and wherein the liquid is configured to be channeled to the at least one pre-heater so that heat is transferred from the liquid to supply air within the supply air flow path before the supply air encounters the energy recovery device.   
     
     
         2 . The system of  claim 1 , further comprising one or more of pipes, tubes, conduits, or plenum connected between the heat transfer device and the heater, wherein the flue gas is configured to pass from the heater to the heat transfer device via the one or more of pipes, tubes, conduits, or plenum. 
     
     
         3 . The system of  claim 1 , wherein the energy exchange system is a Dedicated Outdoor Air System (DOAS). 
     
     
         4 . The system of  claim 1 , wherein the energy recovery device is one or more of an enthalpy wheel, a sensible wheel, a desiccant wheel, a plate heat exchanger, a plate energy exchanger, a heat pipe, or a run-around loop. 
     
     
         5 . The system of  claim 1 , further comprising a heat exchanger, wherein the heat exchanger comprises the heater and at least one radiator coil configured to contain a heat transfer liquid, wherein the at least one radiator coil is configured to be disposed within or around a portion of the supply air flow path. 
     
     
         6 . The system of  claim 5 , wherein the heat exchanger is a liquid-to-gas heat exchanger. 
     
     
         7 . The system of  claim 5 , wherein the heat exchanger comprises one or more of a parallel flow heat exchanger, a counter flow heat exchanger, or a cross flow heat exchanger. 
     
     
         8 . The system of  claim 1 , wherein the at least one pre-heater comprises a liquid-circulating coil in fluid communication with the heat transfer device, wherein the liquid-circulating coil is configured to be disposed within or around a portion of the supply air flow path. 
     
     
         9 . The system of  claim 1 , further comprising a liquid-circulating coil configured to be disposed within or around a flue gas passage, wherein the liquid-circulating coil is configured to receive vented flue gas from the heater, and wherein the liquid-circulating coil is configured to be in fluid communication with the pre-heater. 
     
     
         10 . The system of  claim 1 , wherein the heater is configured to be downstream from the energy recovery device within the supply air flow path. 
     
     
         11 . The system of  claim 1 , wherein the heater is configured to be upstream from the energy recovery device within the supply air flow path. 
     
     
         12 . The system of  claim 1 , further comprising at least one additional heat exchanger operatively connected to the heat transfer device. 
     
     
         13 . The system of  claim 1 , further comprising at least one return air duct configured to fluidly connect the supply air flow path with the exhaust air flow path. 
     
     
         14 . The system of  claim 1 , wherein the heat transfer device is remote from the heater and the pre-heater. 
     
     
         15 . The system of  claim 1 , wherein energy from the flue gas prevents frost from forming on the energy recovery device. 
     
     
         16 . The system of  claim 1 , further comprising at least one bypass duct configured to be disposed within the supply air flow path, wherein the at least one bypass duct is configured to bypass at least a portion of the supply air around one or both of the pre-heater or the energy recovery device. 
     
     
         17 . The system of  claim 1 , wherein the heat transfer device and the heater are disposed within a common housing. 
     
     
         18 . A method of operating a Dedicated Outdoor Air System having a supply air flow path that allows supply air to be supplied to an enclosed structure and an exhaust air flow path that allows exhaust air from the enclosed structure to be exhausted to the atmosphere, the method comprising:
 capturing flue gas generated by a heater;   channeling the flue gas to a heat transfer device;   transferring heat from the flue gas to liquid within the heat transfer device;   circulating the liquid to a pre-heater; and   transferring heat within the liquid to supply air within the supply air flow path.   
     
     
         19 . The method of  claim 18 , further comprising venting the flue gas from the heat transfer device after heat from the flue gas has been transferred to the liquid within the heat transfer device. 
     
     
         20 . The method of  claim 18 , further comprising recirculating the liquid back to the heat transfer device after the heat within the liquid has been transferred to the supply air. 
     
     
         21 . The method of  claim 18 , further comprising passing the heated supply air to an energy recovery device after the heat within the liquid has been transferred to the supply air. 
     
     
         22 . The method of  claim 21 , further comprising preventing frost from forming on the energy recovery device through the channeling operation. 
     
     
         23 . The method of  claim 18 , further comprising bypassing at least a portion of the supply air around one or both of the pre-heater or an energy recovery device. 
     
     
         24 . A Dedicated Outdoor Air System (DOAS) comprising:
 a heater configured to be disposed within a supply air flow path;   a pre-heater configured to be upstream from the heater within the supply air flow path; and   a heat transfer device operatively connected to the heater and the pre-heater, wherein the heat transfer device is configured to receive flue gas from the heater and transfer heat from the flue gas to liquid within the heat transfer device, and wherein the liquid is configured to be channeled to the pre-heater so that heat is transferred from the liquid to supply air within the supply air flow path.